Connectivity In Wireless Networks Research Articles

A novel connectivity and coverage algorithm based on shortest path for wireless sensor networks

A novel shortest path connectivity and coverage algorithm (SPCCA) for wireless sensor networks is proposed to reduce the energy consumption and to extend the network lifetime. The main procedure of SPCCA is as follows: first, each node determines whether it is the redundant node. Then, the redundant nodes enter into the ready-to-sleep mode through the node selection method and the sleepless nodes enter into the active mode. In this way, the blind spot can be avoided and the energy balance can be guaranteed. Finally, the redundant nodes on the shortest path are woken up in order to guarantee the connectivity of the network. Simulation results show that the number of working nodes of SPCCA is stable and they do not increase with the number of the deployed nodes. Moreover, SPCCA has better performance than most homogeneous algorithms in terms of the network coverage, connectivity, connection cost and network lifetime.

Survey on Monitoring and Quality Controlling of the Mobile Biosignal Delivery.

A Mobile Patient Monitoring System (MPMS) acquires patient's biosignals and transmits them using wireless network connection to the decision-making module or healthcare professional for the assessment of patient's condition. A variety of wireless network technologies such as wireless personal area networks (e.g., Bluetooth), mobile ad-hoc networks (MANET), and infrastructure-based networks (e.g., WLAN and cellular networks) are in practice for biosignals delivery. The wireless network quality-of-service (QoS) requirements of biosignals delivery are mainly specified in terms of required bandwidth, acceptable delay, and tolerable error rate. An important research challenge in the MPMS is how to satisfy QoS requirements of biosignals delivery in the environment characterized by patient mobility, deployment of multiple wireless network technologies, and variable QoS characteristics of the wireless networks. QoS requirements are mainly application specific, while available QoS is largely dependent on QoS provided by wireless network in use. QoS provisioning refers to providing support for improving QoS experience of networked applications. In resource poor conditions, application adaptation may also be required to make maximum use of available wireless network QoS. This survey paper presents a survey of recent developments in the area of QoS provisioning for MPMS. In particular, our contributions are as follows: (1) overview of wireless networks and network QoS requirements of biosignals delivery; (2) survey of wireless networks' QoS performance evaluation for the transmission of biosignals; and (3) survey of QoS provisioning mechanisms for biosignals delivery in MPMS. We also propose integrating end-to-end QoS monitoring and QoS provisioning strategies in a mobile patient monitoring system infrastructure to support optimal delivery of biosignals to the healthcare professionals.

Reducing hops without extra power: Impact of deployment height on low-power multihop wireless network

Many low-power wireless network system deployments are planned on a two-dimensional plane, while in reality, we live in a three-dimensional space. Therefore, although it is essential to well consider the impact of height on the overall wireless system performance, this aspect has often been overlooked if not neglected with simplifying assumptions. Our work takes an empirical effort in quantifying the impact of height on a low-power wireless system’s performance. Specifically, we use CC2420 radio–based wireless sensor network motes to quantify the impact of device deployment height on the connectivity and energy efficiency of low-power wireless networks. In addition, to validate the newly proposed sub-GHz low-power radios, we also experiment on the performance of CC1200 narrowband low-power radios to show that increasing a small amount of height in the node deployment phase can lead to drastic improvements in radio coverage and packet delivery performance. Such an observation can naturally lead to the reduction of network depth in a multihop wireless network for a given target deployment field; thus, it can potentially improve the energy efficiency of the overall system by suppressing the number of packet relay transmissions. We support our findings and observations through experiments on real embedded devices.

Dispersion with connectivity in wireless mesh networks

We study a multi-objective access point dispersion problem, where the conflicting objectives of maximizing the distance and maximizing the connectivity between the agents are considered with explicit coverage (or Quality of Service) constraints. We model the problem first as a multi-objective model, and then, we consider the constrained single objective alternatives, which we propose to solve using three approaches: The first approach is an optimal tree search algorithm, where bounds are used to prune the search tree. The second approach is a beam search heuristic, which is also used to provide lower bound for the first approach. The third approach is a straightforward integer programming approach. We present an illustrative application of our solution approaches in a real wireless mesh network deployment problem.

Distributed cell selection in heterogeneous wireless networks

A critical issue in many wireless networks is how to establish the best possible quality connections between users to base stations. This is in particular challenging when users are randomly located over a geographical region, and each covered by a number of heterogeneous base stations. To this end, we design a smart and efficient cell selection mechanism to improve the user-base station connection in heterogeneous wireless networks. We formulate the cell selection problem as an asymmetric congestion game with consideration of users’ heterogeneity in their locations and their data rates to various cells. We show the existence of pure Nash equilibria (PNE) and propose a concurrent distributed learning algorithm to converge to them. In the algorithm, we allow users to perform random error-tolerant updates synchronously, and guarantee them to reach one or multiple PNE with the largest utilities. In addition, we do a systematical investigation on the implementation of the algorithm in practical networks. Simulation results show that the algorithm can achieve satisfactory performance with acceptable convergence rate.

Establishing symmetric connectivity in directional wireless sensor networks equipped with $$2\pi /3$$ 2 π / 3 antennas

In this paper, we study the antenna orientation problem concerning symmetric connectivity in directional wireless sensor networks. We are given a set of nodes each of which is equipped with one directional antenna with beam-width $$\theta = 2\pi /3$$ and is initially assigned a transmission range 1 that yields a connected unit disk graph spanning all nodes. The objective of the problem is to compute an orientation of the antennas and to find a minimum transmission power range $$r=O(1)$$ such that the induced symmetric communication graph is connected. We propose two algorithms that orient the antennas to yield symmetric connected communication graphs where the transmission power ranges are bounded by 6 and 5, which are currently the best results for this problem. We also study the performance of our algorithms through simulations.

On Connectivity of Wireless Sensor Networks with Directional Antennas.

In this paper, we investigate the network connectivity of wireless sensor networks with directional antennas. In particular, we establish a general framework to analyze the network connectivity while considering various antenna models and the channel randomness. Since existing directional antenna models have their pros and cons in the accuracy of reflecting realistic antennas and the computational complexity, we propose a new analytical directional antenna model called the iris model to balance the accuracy against the complexity. We conduct extensive simulations to evaluate the analytical framework. Our results show that our proposed analytical model on the network connectivity is accurate, and our iris antenna model can provide a better approximation to realistic directional antennas than other existing antenna models.

Wildfire Monitoring and Detection System Using Wireless Sensor Network: A Case Study of Tanzania

This paper proposes a wildfire monitoring and detection system based on wireless sensor network. This system detects fire by monitoring surrounding temperature, humidity and smoke. Once fire is detected, a warning message containing probable location of that fire is immediately sent to the responsible authority over cellular network. In order for the system to be more effective, communities living near forests or national parks can send warning messages through the same system to the responsible authority using their mobile handsets once they witness wildfire or illegal activities. For the system to be fully functional, the only requirement is the availability of cellular network coverage in forests or national parks to enable short message services to take place. The system prototype is developed using Arduino microcontroller, several sensors to detect temperature, relative humidity and smoke as well as wireless network connection modules. At the control center Telerivet messaging platform is used to design the messaging service. The experimental results justify the capability of the proposed system in detecting wildfire in real time.

Node Service Ability Aware Packet Forwarding Mechanism in Intermittently Connected Wireless Networks

Intermittently connected wireless networks (ICWNs) have been studied in recent years to solve the disruption problem in mobile ad hoc networks and improve the utilization of temporary links raised by node movements. In ICWNs, the packet storing-carrying-forwarding principle is adopted through the cooperation between multiple nodes. Therefore, it is critical to include the connection status of nodes in designing efficient packet forwarding mechanism. In this paper, a node service ability aware packet forwarding mechanism is proposed based on the connection status. First, the connection model is established to analyze the transition of connection status; moreover, the service ability can be evaluated according to the connection strength and connection availability. Second, packet forwarding levels are determined based on their transmitting status to exploit the limited buffer resources. Consequently, the efficient packet forwarding mechanism can guarantee the flexibility of packet transmission in both complex and dynamic network scenarios. Numerical results show that about 20% delivery ratio increase can be achieved by the proposed mechanism, while the overheads and latency are reduced.

Mitigation of black hole attacks in Routing Protocol for Low Power and Lossy Networks

AbstractRouting Protocol for Low Power and Lossy Networks (RPL) has been standardized by the Internet Engineering Task Force to efficiently manage the functions of the network layer when providing Internet connectivity for wireless sensor networks. RPL has been designed for constrained devices and networks. Owing to their constrained nature, RPL‐based networks can be exposed to a wide variety of security attacks. One of the most serious attacks in RPL is a black hole attack, where a malicious node silently drops all the packets that it is supposed to forward. This paper proposes a mitigation technique against black hole attack with low packet loss and high reliability. The proposed technique consists of a local decision and a global verification process. First, each node observes the communication behavior of its neighboring nodes by overhearing packets transmitted by its neighbors and attempts to identify suspicious nodes based on their behavior. In the second process, if a node identifies a suspicious node, then it verifies whether the suspicious node is a black hole. We demonstrate that the proposed approach increases packet delivery rate significantly and detects black hole attack effectively. Copyright © 2016 John Wiley & Sons, Ltd.

Analytical framework for the characterization of the link properties in multi-hop mobile wireless networks

The maintainability of connectivity in multi-hop mobile wireless networks is a complex task to achieve, for which various factors must be taken into account in order to avoid link failures. In addition to the bandwidth limitation, node mobility and interference are two aspects that impact directly the reliability of the communication link, leading generally to loss of wireless link connectivity. In this paper, we develop an analytical framework which determines the link and path lifetime in multi-hop mobile wireless networks. Through this model, we derive an analytical model of the link and path lifetime by taking into consideration both node mobility and interference. We find that the probability density function (PDF) of the duration of a link in presence of interference can be approximated by an exponential distribution with parameter λ which relies the transmission range R, the average speed V¯, the Signal-to-Interference-Plus-Noise-Ratio (SINR) threshold β, the path loss exponent α, and the maximum number of interfering nodes N. We extend this model to evaluate the PDF of the link lifetime by taking into account both interference and mobility of the linked nodes. We conclude that the PDF of the overall link lifetime can be approximated by a Rayleigh distribution that is in harmony with several previous simulation based-studies. Furthermore, some properties of wireless links and multi-hop paths are evaluated and several simulations are carried out in order to investigate the multi-hop wireless network connectivity and the associated performance.

Accelerating task completion in mobile offloading systems through adaptive restart

Mobile application offloading is an efficient technique to unload the burden of intensive computation from thin clients to powerful servers. In a mobile offloading system, cloud computing is utilized to complete some heavy tasks which are migrated from resource-constrained mobile devices to the Cloud. To assure system performance, the quality of the wireless network connection plays an important role. In previous work we experimentally explored the impact of packet loss and delay in wireless networks on the completion time of an offloading task. We investigated a local restart mechanism to mitigate these effects. In the presence of unreliable communication, once the waiting time for the response of a cloud server exceeds a given threshold, exploiting the local resources of a mobile client can accelerate the task completion.

Detecting Colluding Blackhole and Greyhole Attacks in Delay Tolerant Networks

Delay Tolerant Network (DTN) is developed to cope with intermittent connectivity and long delay in wireless networks. Due to the limited connectivity, DTN is vulnerable to blackhole and greyhole attacks in which malicious nodes intentionally drop all or part of the received messages. Although existing proposals could accurately detect the attack launched by individuals, they fail to tackle the case that malicious nodes cooperate with each other to cheat the defense system. In this paper, we suggest a scheme called Statistical-based Detection of Blackhole and Greyhole attackers (SDBG) to address both individual and collusion attacks. Nodes are required to exchange their encounter record histories, based on which other nodes can evaluate their forwarding behaviors. To detect the individual misbehavior, we define forwarding ratio metrics that can distinguish the behavious of attackers from normal nodes. Malicious nodes might avoid being detected by colluding to manipulate their forwarding ratio metrics. To continuously drop messages and promote the metrics at the same time, attackers need to create fake encounter records frequently and with high forged numbers of sent messages. We exploit the abnormal pattern of appearance frequency and number of sent messages in fake encounters to design a robust algorithm to detect colluding attackers. Extensive simulation shows that our solution can work with various dropping probabilities and different number of attackers per collusion at high accuracy and low false positive.

Optimal relay placement in multi-hop wireless networks

Relay node placement in wireless environments is a research topic recurrently studied in the specialized literature. A variety of network performance goals, such as coverage, data rate and network lifetime, are considered as criteria to lead the placement of the nodes. In this work, a new relay placement approach to maximize network connectivity in a multi-hop wireless network is presented. Here, connectivity is defined as a combination of inter-node reachability and network throughput. The nodes are placed following a two-step procedure: (i) initial distribution, and (ii) solution selection. Additionally, a third stage for placement optimization is optionally proposed to maximize throughput. This tries to be a general approach for placement, and several initialization, selection and optimization algorithms can be used in each of the steps. For experimentation purposes, a leave-one-out selection procedure and a PSO related optimization algorithm are employed and evaluated for second and third stages, respectively. Other node placement solutions available in the literature are compared with the proposed one in realistic simulated scenarios. The results obtained through the properly devised experiments show the improvements achieved by the proposed approach.

Implementation of an efficient algorithm to enhance connectivity and lifetime in wireless sensor networks

Implementation of an efficient algorithm to enhance connectivity and lifetime in wireless sensor networks

Connectivity with directional antennas in the symmetric communication model

We study the problem of connectivity in wireless networks in which each node uses a single directional antenna. We consider the symmetric model of communication with directional antennas. In this model, two nodes are connected by a link if and only if they lie in the transmission sectors of each other's antenna. Given nodes located in the plane, each with an antenna of beamwidth ϕ and radius r, we study the problem of orienting the antennas in such a way as to create a connected network. We show that for ϕ<π/3 and a given radius, the problem of determining the existence of an orientation that ensures a connected network is NP-complete. For ϕ≥π/2, in which case connectivity is known to be always possible, we study the problem of achieving connectivity while minimizing the radius. For different ranges of ϕ, we give approximation algorithms that achieve connectivity while using a radius that is at most a constant times the optimal radius. Some of our algorithms also have provable bounds on the stretch factor of the resulting network compared to a network of nodes with omnidirectional antennas of a given radius.

Video Quality-Based Spectral and Energy Efficient Mobile Association in Heterogeneous Wireless Networks

The staggering mobile growth is shaping to be the biggest shift in technology since the advent of the Internet, paving the way for unprecedented and yet to be thought of video services and applications. The proliferation of these mobile devices and applications, however, requires new paradigms to satisfy the increasing demands for capacity and energy, and achieve a good video quality. In this paper, we propose a video quality-based framework for spectrum and energy efficient mobile association and resource allocation in heterogeneous wireless networks. The basic tenets of the framework are (1) two novel performance metrics, namely QSE and QEE, to capture spectrum usage and energy consumption from video quality's perspective; and (2) a computationally efficient optimization model to derive mobile association and resource allocation for video connections in heterogeneous wireless networks. To this end, we first study the fundamental tradeoff between QSE and QEE in a PtP Rayleigh fading wireless channel. We then study QSE and QEE at the system level and develop a mobile association and resource allocation scheme that aims to jointly optimize system level QSE and QEE. The problem is formulated as a mixed-integer nonlinear optimization problem. Nonlinear fractional programming approach and dual decomposition method are applied to search the optimal solutions in a computationally efficient way. The simulation results evaluate the performance tradeoff between QSE and QEE, and show that the system performance, including PSNR distribution and maximum QSE/QEE values, greatly depends on bandwidth and power decaying factors.

Connectivity of wireless sensor networks in greenhouse for plant growth

Wireless sensor networks have been applied in farmland and greenhouse. However, poor connectivity always results in a lot of nodes isolation in the network in a scenario. For this reason, the network connectivity is worth considering to improve its quality, especially when the collected data cannot be sent to the data center because of the obstacles such as the growth of crop plants and weeds. Therefore, how to reduce the effect of crop growth on network connectivity, and enable the reliable transmission of field information, are the key problems to be resolved. To solve these problems, the method which adds long distance routing nodes to the WSN to reduce the deterioration of WSN connectivity during the growth of plants was proposed. To verify this method, the network connectivity of the deployed WSN was represented by the rank of connection matrix based on the graph theory. Consequently, the rank with value of 1 indicates a fully connected network. Moreover, the smaller value of rank means the better connectedness. In addition, the network simulator NS2 simulation results showed that the addition of long-distance backup routing nodes can improve the network connectivity. Furthermore, in experiments, using ZigBee-based wireless sensor network, a remote monitoring system in greenhouse was established, which can obtain environmental information for crops, e.g. temperature, humidity, light intensity and other environmental parameters as well as the wireless link quality especially. Experimental results showed adding of long-distance backup routing nodes can guarantee network connectivity in the region where received signal strength indication (RSSI) was poor, i.e. RSSI value was less than −100 dBm, and the energy was low. In conclusion, this method was essential to improve the connectivity of WSN, and the optimized method still needs further research. Keywords: wireless sensor network, network connectivity, long-distance route nodes, received signal strength indication (RSSI), greenhouse DOI: 10.3965/j.ijabe.201606901.1314 Citation: Chen Y, Shi Y L, Wang Z Y, Huang L. Connectivity of wireless sensor networks for plant growth in greenhouse. Int J Agric & Biol Eng, 2016; 9(1): 89－98.

On the Fast Fading Gaussian Wiretap Channel With Statistical Channel State Information at the Transmitter

In this paper, we investigate the ergodic secrecy capacity of the fast fading Gaussian wiretap channel when only the statistics of the channel state information are known at the transmitter. We derive conditions for the existence of degradedness and a positive ergodic secrecy capacity under the usual stochastic order, the convex order, and the increasing convex order between the legitimate and eavesdropper channels. For more general orders, we prove the secrecy capacity of layered erasure wiretap channels and propose a layered signaling for the achievable scheme, and we derive an upper bound on the capacity for fast fading Gaussian wiretap channels. Finally, the numerical results show that under Nakagami-m fast fading channels, the proposed layered signaling outperforms the Gaussian codebook in several cases. In particular, in certain cases, the Gaussian codebook can achieve only a zero secrecy rate, whereas the proposed scheme achieves positive secrecy rates. Therefore, the connectivity of wireless networks can be significantly improved by the proposed scheme.

A range-free localisation algorithm based on connectivity in wireless sensor networks

Sensor nodes' position is very important in many wireless sensor networks WSNs applications. In this paper, a novel range-free localisation algorithm based on connectivity LAC is proposed. By exploiting the probabilistic regulation in cluster-based deployment, the theoretical number of a sensor's neighbours from certain cluster is determined by distance between the sensor and the corresponding cluster head. So distances between sensors and cluster heads can be derived by minimising the deviation between the theoretical number of neighbour sensors and the measurement. Using the optimal distance to each cluster head, the position of each sensor can be estimated with maximum likelihood ML multilateration. Compared with some existing range-free algorithms, LAC performs better in terms of localisation accuracy, especially in beacon-less scenarios and reduces communication overhead and computation complexity to some extent. Extensive simulations are performed and the results are observed to be in good consistence with theoretical analysis.